1. Field of the Invention
The present invention relates to a rotary compressor, in particular, to a rotary compressor using journal bearings in a bearing section for supporting its revolving parts.
2. Description of the Prior Art
There is known a rotary compressor in which a rotary comprssion mechanism to suck, compress and discharge gases and a motor to drive it are interlocked together with a journal and incorporated in a single housing. Conventionally the rotary compressor has been widely used for a refrigerator, air conditioner, etc. Since it is relatively easy to minaturize, and also because it is easy to control its compression capacity by means of the variable speed control of the motor.
In recent years, it has been hoped that the rotary compressor can cope with a high-speed rotation of the motor to widen the compression capacity. For performing the high-speed operation of rotary compressors or increasing the rotating speed of motors, any mechanical vibration in the bearing section must be reduced sufficiently and also the durability of the bearing section should be increased.
For the reduction in vibration, it has been known to provide a balancer on a journal so as to compensate for a rotation unbalance of the revolving parts because rolling pistons are eccentrically provided on the revolving parts. Furthermore, for the durability of the bearing section, journal bearings have been used more than ball bearings as the bearing section. A journal bearing is designed to interpose an oil film in a gap between the journal and the journal bearing. The oil film lubricates a mechanical friction surface between the journal and the journal bearing. In the bearing section, an oil groove is defined on the outer surface of the journal or the inner surface of the journal bearing in the axial direction. A lubricating oil is induced to the oil groove and then spreads to the whole bearing surface for making the oil film.
However, another problem remains in the conventional rotary compressor using the journal bearing. That is, the journal deflects in a direction perpendicular to the axis of the journal during its rotation. Because the journal receives centrifugal forces of the piston and the balancer which are both eccentrically mounted on the journal at different axial positions, there exist dynamic inbalances along the length of the journal and the deflection of the journal increases as the rotation speed of the journal increases so that the journal makes contact with the journal bearing against the oil film. Therefore, the deflection of the journal badly effects the bearing section. The deflection of the journal is shown in FIG. 5 and will be described in detail later.
It was difficult to avoid the contact between the journal bearing and the journal in the conventional rotary compressor, and for this reason there were problems that the operating efficiency is lowered, the durability is also deteriorated, and in the worst case it provokes a baking damage of the bearing section.